Large wheel base types of machines, such as motor graders, may have hydrostatic drive systems for driving the rear wheels or tracks, whereas the front wheels are used for steering. The hydrostatic drive system may include multiple hydraulic circuits associated with respective wheels or tracks. It is generally desired to maintain a pressure balance between the multiple hydraulic circuits.
During operations, there may be pressure fluctuations and imbalance between the individual hydraulic circuits of the hydrostatic drive system, due to size of the wheels, calibration errors, or fluid leakage etc. The pressure imbalance in these hydraulic circuits may cause unnecessary turning of the machine. Further, in machines, where the front wheels are only used for steering purposes and are hydraulically non-powered, an operator may tend to compensate for the pressure imbalance by manually steering the front wheels without realizing the pressure imbalance between the hydraulic circuits driving the rear wheels. This may result in loss of efficiency of the machine and energy loss in the hydrostatic drive system.
Conventionally, a speed feedback mechanism, using speed sensors, is used to maintain the pressure balance. However, using speed sensors may not be effective for the machines where the front wheels are used for steering purposes, as an error in the speed may not be realized because the operator may compensate for the pressure imbalance by steering.
U.S. Pat. No. 8,347,618 relates to a dual pump hydraulic system for a vehicle driven by an internal combustion engine. The system includes a first circuit with a first high pressure pump supplying hydraulic fluid to the first subsystem at a higher pressure. The system also includes a second circuit with a second lower pressure pump supplying hydraulic fluid to the second subsystem at a second pressure. A first valve controls communication between the first pump and the second circuit. A second valve is operable to communicate the second pump with the first circuit when pressure in the first circuit is less than a second threshold pressure or when commanded by a control unit. A check valve prevents fluid flow from the first circuit back into to the second valve.
However, using pressure balance valves is also not effective, as there may be loss of pressure and efficiency and also, the pressure balance valves are expensive to implement. Therefore, there is a need for an improved system and method to maintain pressure balance between the hydraulic circuits in the hydrostatic drive system.